diff --git a/libcxx/benchmarks/CMakeLists.txt b/libcxx/benchmarks/CMakeLists.txt
--- a/libcxx/benchmarks/CMakeLists.txt
+++ b/libcxx/benchmarks/CMakeLists.txt
@@ -166,6 +166,11 @@
 # Register Benchmark tests
 #==============================================================================
 file(GLOB BENCHMARK_TESTS "*.bench.cpp")
+
+if (NOT LIBCXX_ENABLE_INCOMPLETE_FEATURES)
+  list(FILTER BENCHMARK_TESTS EXCLUDE REGEX "(format_to_n|format_to|format|formatted_size|formatter_float|std_format_spec_string_unicode).bench.cpp")
+endif()
+
 foreach(test_path ${BENCHMARK_TESTS})
   get_filename_component(test_file "${test_path}" NAME)
   string(REPLACE ".bench.cpp" "" test_name "${test_file}")
diff --git a/libcxx/include/__debug b/libcxx/include/__debug
--- a/libcxx/include/__debug
+++ b/libcxx/include/__debug
@@ -29,10 +29,10 @@
 #   define _LIBCPP_ASSERT_IMPL(x, m) ((void)0)
 #elif _LIBCPP_DEBUG_LEVEL == 1
 #   define _LIBCPP_DEBUG_ASSERT(x, m) ((void)0)
-#   define _LIBCPP_ASSERT_IMPL(x, m) ((x) ? (void)0 : _VSTD::__libcpp_debug_function(_VSTD::__libcpp_debug_info(__FILE__, __LINE__, #x, m)))
+#   define _LIBCPP_ASSERT_IMPL(x, m) ((x) ? (void)0 : ::std::__libcpp_debug_function(::std::__libcpp_debug_info(__FILE__, __LINE__, #x, m)))
 #elif _LIBCPP_DEBUG_LEVEL == 2
-#   define _LIBCPP_DEBUG_ASSERT(x, m) _LIBCPP_ASSERT(__libcpp_is_constant_evaluated() || (x), m)
-#   define _LIBCPP_ASSERT_IMPL(x, m) ((x) ? (void)0 : _VSTD::__libcpp_debug_function(_VSTD::__libcpp_debug_info(__FILE__, __LINE__, #x, m)))
+#   define _LIBCPP_DEBUG_ASSERT(x, m) _LIBCPP_ASSERT(::std::__libcpp_is_constant_evaluated() || (x), m)
+#   define _LIBCPP_ASSERT_IMPL(x, m) ((x) ? (void)0 : ::std::__libcpp_debug_function(::std::__libcpp_debug_info(__FILE__, __LINE__, #x, m)))
 #else
 #   error _LIBCPP_DEBUG_LEVEL must be one of 0, 1, 2
 #endif
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -2,7 +2,8 @@
 // since __config may be included from C headers which may create an
 // include cycle.
 module std_config [system] [extern_c] {
-    header "__config"
+  textual header "__config"
+  textual header "__config_site"
 }
 
 module std [system] {
diff --git a/libcxx/test/configs/llvm-libc++-shared-clangcl.cfg.in b/libcxx/test/configs/llvm-libc++-shared-clangcl.cfg.in
--- a/libcxx/test/configs/llvm-libc++-shared-clangcl.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-shared-clangcl.cfg.in
@@ -5,7 +5,7 @@
 
 config.substitutions.append(('%{flags}', '--driver-mode=g++'))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX'
+    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS'
 ))
 config.substitutions.append(('%{link_flags}',
     '-nostdlib -L %{lib} -lc++ -lmsvcrt -lmsvcprt -loldnames'
diff --git a/libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in b/libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in
--- a/libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in
+++ b/libcxx/test/configs/llvm-libc++-static-clangcl.cfg.in
@@ -5,7 +5,7 @@
 
 config.substitutions.append(('%{flags}', '--driver-mode=g++'))
 config.substitutions.append(('%{compile_flags}',
-    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -DNOMINMAX'
+    '-nostdinc++ -isystem %{include} -isystem %{target-include} -I %{libcxx}/test/support -D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS'
 ))
 config.substitutions.append(('%{link_flags}',
     '-nostdlib -L %{lib} -llibc++ -lmsvcrt -lmsvcprt -loldnames'
diff --git a/libcxx/test/libcxx/algorithms/debug_less.pass.cpp b/libcxx/test/libcxx/algorithms/debug_less.pass.cpp
--- a/libcxx/test/libcxx/algorithms/debug_less.pass.cpp
+++ b/libcxx/test/libcxx/algorithms/debug_less.pass.cpp
@@ -16,6 +16,7 @@
 
 struct DebugException {};
 
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined
 #define _LIBCPP_DEBUG 0
 #define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : throw ::DebugException())
 
diff --git a/libcxx/test/libcxx/debug/debug_abort.pass.cpp b/libcxx/test/libcxx/debug/debug_abort.pass.cpp
--- a/libcxx/test/libcxx/debug/debug_abort.pass.cpp
+++ b/libcxx/test/libcxx/debug/debug_abort.pass.cpp
@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DEBUG=0
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_DEBUG=0
 // UNSUPPORTED: libcxx-no-debug-mode
 
 // Test that the default debug handler aborts the program.
diff --git a/libcxx/test/libcxx/experimental/memory/memory.polymorphic.allocator.class/memory.polymorphic.allocator.mem/db_deallocate.pass.cpp b/libcxx/test/libcxx/experimental/memory/memory.polymorphic.allocator.class/memory.polymorphic.allocator.mem/db_deallocate.pass.cpp
--- a/libcxx/test/libcxx/experimental/memory/memory.polymorphic.allocator.class/memory.polymorphic.allocator.mem/db_deallocate.pass.cpp
+++ b/libcxx/test/libcxx/experimental/memory/memory.polymorphic.allocator.class/memory.polymorphic.allocator.mem/db_deallocate.pass.cpp
@@ -16,6 +16,7 @@
 
 int AssertCount = 0;
 
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined
 #define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : (void)::AssertCount++)
 #define _LIBCPP_DEBUG 0
 #include <experimental/memory_resource>
diff --git a/libcxx/test/libcxx/experimental/memory/memory.resource.adaptor/memory.resource.adaptor.mem/db_deallocate.pass.cpp b/libcxx/test/libcxx/experimental/memory/memory.resource.adaptor/memory.resource.adaptor.mem/db_deallocate.pass.cpp
--- a/libcxx/test/libcxx/experimental/memory/memory.resource.adaptor/memory.resource.adaptor.mem/db_deallocate.pass.cpp
+++ b/libcxx/test/libcxx/experimental/memory/memory.resource.adaptor/memory.resource.adaptor.mem/db_deallocate.pass.cpp
@@ -16,6 +16,7 @@
 
 int AssertCount = 0;
 
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined
 #define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : (void)::AssertCount++)
 #define _LIBCPP_DEBUG 0
 #include <experimental/memory_resource>
diff --git a/libcxx/test/libcxx/input.output/filesystems/class.path/path.itr/iterator_db.pass.cpp b/libcxx/test/libcxx/input.output/filesystems/class.path/path.itr/iterator_db.pass.cpp
--- a/libcxx/test/libcxx/input.output/filesystems/class.path/path.itr/iterator_db.pass.cpp
+++ b/libcxx/test/libcxx/input.output/filesystems/class.path/path.itr/iterator_db.pass.cpp
@@ -10,7 +10,7 @@
 // UNSUPPORTED: windows
 // UNSUPPORTED: libcxx-no-debug-mode
 
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DEBUG=0
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_DEBUG=0
 
 // <filesystem>
 
diff --git a/libcxx/test/libcxx/iterators/advance.debug1.pass.cpp b/libcxx/test/libcxx/iterators/advance.debug1.pass.cpp
--- a/libcxx/test/libcxx/iterators/advance.debug1.pass.cpp
+++ b/libcxx/test/libcxx/iterators/advance.debug1.pass.cpp
@@ -8,7 +8,7 @@
 
 // UNSUPPORTED: c++03
 // UNSUPPORTED: windows
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DEBUG=0
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_DEBUG=0
 // UNSUPPORTED: libcxx-no-debug-mode
 
 // <list>
diff --git a/libcxx/test/libcxx/iterators/next.debug1.pass.cpp b/libcxx/test/libcxx/iterators/next.debug1.pass.cpp
--- a/libcxx/test/libcxx/iterators/next.debug1.pass.cpp
+++ b/libcxx/test/libcxx/iterators/next.debug1.pass.cpp
@@ -8,7 +8,7 @@
 
 // UNSUPPORTED: c++03
 // UNSUPPORTED: windows
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DEBUG=0
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_DEBUG=0
 // UNSUPPORTED: libcxx-no-debug-mode
 
 // <list>
@@ -27,8 +27,8 @@
 
 
     forward_iterator<int *> it(a+1);
-	std::next(it, 1);  // should work fine
-	std::next(it, 0);  // should work fine
+    std::next(it, 1);  // should work fine
+    std::next(it, 0);  // should work fine
     EXPECT_DEATH( std::next(it, -1) ); // can't go backwards on a FwdIter
 
   return 0;
diff --git a/libcxx/test/libcxx/iterators/prev.debug1.pass.cpp b/libcxx/test/libcxx/iterators/prev.debug1.pass.cpp
--- a/libcxx/test/libcxx/iterators/prev.debug1.pass.cpp
+++ b/libcxx/test/libcxx/iterators/prev.debug1.pass.cpp
@@ -8,7 +8,7 @@
 
 // UNSUPPORTED: c++03
 // UNSUPPORTED: windows
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DEBUG=0
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_DEBUG=0
 // UNSUPPORTED: libcxx-no-debug-mode
 
 // <list>
@@ -26,8 +26,8 @@
     int a[] = {1, 2, 3};
 
     bidirectional_iterator<int *> bidi(a+1);
-	std::prev(bidi, -1);  // should work fine
-	std::prev(bidi,  0);  // should work fine
+    std::prev(bidi, -1);  // should work fine
+    std::prev(bidi,  0);  // should work fine
     std::prev(bidi,  1);  // should work fine
 
     forward_iterator<int *> it(a+1);
diff --git a/libcxx/test/libcxx/thread/futures/futures.promise/set_exception.pass.cpp b/libcxx/test/libcxx/thread/futures/futures.promise/set_exception.pass.cpp
--- a/libcxx/test/libcxx/thread/futures/futures.promise/set_exception.pass.cpp
+++ b/libcxx/test/libcxx/thread/futures/futures.promise/set_exception.pass.cpp
@@ -11,7 +11,7 @@
 // UNSUPPORTED: c++03
 // UNSUPPORTED: libcxx-no-debug-mode
 
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DEBUG=0
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_DEBUG=0
 
 // <future>
 
diff --git a/libcxx/test/libcxx/thread/futures/futures.promise/set_exception_at_thread_exit.pass.cpp b/libcxx/test/libcxx/thread/futures/futures.promise/set_exception_at_thread_exit.pass.cpp
--- a/libcxx/test/libcxx/thread/futures/futures.promise/set_exception_at_thread_exit.pass.cpp
+++ b/libcxx/test/libcxx/thread/futures/futures.promise/set_exception_at_thread_exit.pass.cpp
@@ -11,7 +11,7 @@
 // UNSUPPORTED: c++03
 // UNSUPPORTED: libcxx-no-debug-mode
 
-// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DEBUG=0
+// ADDITIONAL_COMPILE_FLAGS: -Wno-macro-redefined -D_LIBCPP_DEBUG=0
 
 // <future>
 
diff --git a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/last_write_time.pass.cpp b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/last_write_time.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/last_write_time.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.obs/last_write_time.pass.cpp
@@ -19,6 +19,9 @@
 // file_time_type last_write_time() const;
 // file_time_type last_write_time(error_code const&) const noexcept;
 
+// Disable min() and max() macros in <windows.h> on Windows.
+// ADDITIONAL_COMPILE_FLAGS: -DNOMINMAX
+
 #include "filesystem_include.h"
 #include <type_traits>
 #include <cassert>
diff --git a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.last_write_time/last_write_time.pass.cpp
@@ -22,6 +22,9 @@
 // void last_write_time(const path& p, file_time_type new_type,
 //                      std::error_code& ec) noexcept;
 
+// Disable min() and max() macros in <windows.h> on Windows.
+// ADDITIONAL_COMPILE_FLAGS: -DNOMINMAX
+
 #include "filesystem_include.h"
 #include <chrono>
 #include <cstdio>
diff --git a/libcxx/test/support/filesystem_test_helper.h b/libcxx/test/support/filesystem_test_helper.h
--- a/libcxx/test/support/filesystem_test_helper.h
+++ b/libcxx/test/support/filesystem_test_helper.h
@@ -31,6 +31,9 @@
 # include <sys/un.h>
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 namespace utils {
 #ifdef _WIN32
     inline int mkdir(const char* path, int mode) { (void)mode; return ::_mkdir(path); }
@@ -733,4 +736,6 @@
   return fs::path();
 }
 
-#endif /* FILESYSTEM_TEST_HELPER_HPP */
+_LIBCPP_POP_MACROS
+
+#endif /* FILESYSTEM_TEST_HELPER_H */
diff --git a/libcxx/utils/libcxx/test/config.py b/libcxx/utils/libcxx/test/config.py
--- a/libcxx/utils/libcxx/test/config.py
+++ b/libcxx/utils/libcxx/test/config.py
@@ -245,10 +245,6 @@
             # Build the tests in the same configuration as libcxx itself,
             # to avoid mismatches if linked statically.
             self.cxx.compile_flags += ['-D_CRT_STDIO_ISO_WIDE_SPECIFIERS']
-            # Required so that tests using min/max don't fail on Windows,
-            # and so that those tests don't have to be changed to tolerate
-            # this insanity.
-            self.cxx.compile_flags += ['-DNOMINMAX']
         additional_flags = self.get_lit_conf('test_compiler_flags')
         if additional_flags:
             self.cxx.compile_flags += shlex.split(additional_flags)
diff --git a/libcxx/utils/libcxx/test/features.py b/libcxx/utils/libcxx/test/features.py
--- a/libcxx/utils/libcxx/test/features.py
+++ b/libcxx/utils/libcxx/test/features.py
@@ -129,22 +129,10 @@
   '_LIBCPP_HAS_NO_UNICODE': 'libcpp-has-no-unicode',
 }
 for macro, feature in macros.items():
-  DEFAULT_FEATURES += [
-    Feature(name=lambda cfg, m=macro, f=feature: f + (
-              '={}'.format(compilerMacros(cfg)[m]) if compilerMacros(cfg)[m] else ''
-            ),
-            when=lambda cfg, m=macro: m in compilerMacros(cfg),
-
-            # FIXME: This is a hack that should be fixed using module maps.
-            # If modules are enabled then we have to lift all of the definitions
-            # in <__config_site> onto the command line.
-            actions=lambda cfg, m=macro: [
-              AddCompileFlag('-Wno-macro-redefined -D{}'.format(m) + (
-                '={}'.format(compilerMacros(cfg)[m]) if compilerMacros(cfg)[m] else ''
-              ))
-            ]
-    )
-  ]
+  DEFAULT_FEATURES.append(
+    Feature(name=lambda cfg, m=macro, f=feature: f + ('={}'.format(compilerMacros(cfg)[m]) if compilerMacros(cfg)[m] else ''),
+            when=lambda cfg, m=macro: m in compilerMacros(cfg))
+  )
 
 
 # Mapping from canonical locale names (used in the tests) to possible locale